Traffic shaping, or bandwidth throttling, remains a hot issue in the BitTorrent community. In an effort to reduce network traffic and costs, some ISPs have strictly limited the bandwidth available to P2P traffic. Customers of Canadian ISPs have long complained that bandwidth available to their favorite file-sharing networks – especially BitTorrent – have been throttled to the point of near futility.

The justification for limiting bandwidth to P2P protocols, from an ISPs perspective, is simple. File-sharing traffic has grown considerably over the last several years, generated by the insatiable activities of the BitTorrent and eDonkey2000 community. According to some estimates, up to 60% or more of an ISPs bandwidth may be consumed by such protocols.

ISPs are stuck between two difficult situations; please their customers or mitigating their costs. Throttling available bandwidth to a point of negligibility has proven very unpopular. Simply ignoring the problem doesn’t work either. For smaller ISPs, simply upgrading their network has its financial limitations. Caching P2P traffic has gained acceptance from consumers and some ISPs, yet small ISPs may have trouble justifying such a solution on a small network.

File-sharing developers have rushed to respond to the once prominent threat of bandwidth throttling by introducing clients equipped with end to end encryption. Most notably, BitComet, Azureus, and eMule – among the most popular of file-sharing applications – have been armed with this feature. Although bandwidth throttling is no longer the imminent threat it once was, as ISPs have begun adopting alternative solutions, the practice remains a legitimate concern for millions of file-sharers.

Therefore it was little surprise when an outburst of anxiety accompanied Australian ISP Exetel’s notification that the company would begin reducing available bandwidth to P2P users.

“From mid November, approximately, Exetel will restrict the amount of bandwidth it provides to P2P traffic to approximately 50% of what all aggregated users of P2P protocols could at any single point in time, theoretically, use during the period 12 noon to 12 midnight each day. It should be understood that "theoretically use" is almost never possible because of the inherent constraints of P2P operating scenarios,” the announcement from Extel read.

The above quote from Exetel’s forum post would immediately have any prolific BitTorrent or eDonkey2000 fan searching for a new ISP. Would my available bandwidth drop from 512K to 256K? Are my P2P activities going to be pushed off the network? Doesn’t Exetel realize that my BitTorrent client is like a family pet?

“We have not considered caching solutions yet,” James Linton of Exetel told Slyck.com. “Our first reason is that we have an immediate issue with the introduction of ADSL2 (Australia until very recently has had a limit of 1500 kbps on ADSL1 services.) The early indications, for us at least, are that the ‘early adopters’, both in our own current ADSL1 customers transferring to ADSL2 and to new users joining our network, is that they will very heavily use P2P and the ‘leap’ from 1,500 kbps traffic downloads to in excess of 6,000 kbps traffic downloads for a growing percentage of our user base will ‘send us broke’ if we attempted to meet that raw demand in peak bandwidth use or totally disenchant our other 40,000 plus users if we allowed the network to become contended for significant portions of the day.”

As pointed out by Mr. Linton, running cache servers is no cheap affair. Cache servers may reduce ISP’s bandwidth cost by keeping the most sought files within an ISP’s network – however considering the size of most files transferred via BitTorrent, this solution is incompatible with the desire to mitigate Exetel’s cost.

Exetel has also taken into consideration the fact that protocol encryption has become a popular countermeasure to bandwidth throttling. Mindful of this, Exetel has implemented its own countermeasures.

“We will use the Allot NetEnforcer 2520. We have run extensive testing of the next model down, which we were loaned by the Australian distributor, over a 2 month period to test its ability to detect current levels of encryption. The tests have been very successful over that period and we are, at this time, satisfied that the Allot engineers will be able to continue to deal with new levels of packet obfuscation as they are, inevitably, developed. However that is an assumption on our part based on our relatively limited experiences to date.”

A concerned Exetel BitTorrent may read their ISP’s notice, their current position on caching and the implementation of protocol encryption countermeasures and say, “My BitTorrent days are over!”

Not quite.

Exetel’s James Linton has spent considerable time explaining that unlike other ISPs that may reduce P2P bandwidth to a mere fraction of the network’s potential, Exetel is working with P2P users to ensure that everyone’s Internet experience is enjoyable.

But wait a second Slyck, Exetel just said the amount of bandwidth available to P2P traffic will be cut in half for 12 hours a day!

That certainly appears to be the case. But it’s important to carefully read Exetel’s position and understand exactly what the statement says. For arguments sake, let’s assume that a BitTorrent user is downloading at 6:00 PM with 1,500 kbps of available download bandwidth – right in the middle of Exetel’s bandwidth adjustment.

Does this mean this user’s download speed will drop from 1,500 kbps to 750 kbps? Not necessary. In order for that to happen, the bandwidth allotted to P2P traffic would have to be completely saturated. If file-sharing traffic remains stable, and plenty of reserve bandwidth is still available, chances are the user will still download at a high rate. If many downloaders absorb a tremendous amount of bandwidth, say an individual who continuously downloads 24 hours a day, then it is likely some noticeable decrease in download speed will occur.

Another portion of Exetel’s statement to examine with a microscope is the word “theoretical.” As many BitTorrent users can attest, it is an infrequent event when download speeds are maximized. In other words, under optimum network connections; say when the aggregate (collective) BitTorrent Exetel users have all connected to seeds with fiber optic T3 connections, will the downloader notice a reduction in download speed. When this BitTorrent collective is utilizing the maximum bandwidth available, Extel’s network controls will be implemented. However, these circumstances are infrequent and should not have an adverse affect on the end user’s BitTorent experience.

“Firstly, as we have not deployed the full P2P traffic controls yet no “user” can have any experience of what the result will be and therefore any “complaints” (and please bear in mind that the overwhelming majority of the forum posts on the Australian site “Whirlpool” have not been from Exetel customers) are based on NO actual experience; well, no experience the few actual Exetel customers have been aware of. In fact the trials of the smaller Allot box have been, as I previously stated, in operation for the past 2 months and, prior to that, we used a far less sophisticated solution of running rate limiting of the heaviest down loaders via ‘lists’ on Cisco core routers for well over a year.”

“The tests have been quite severely constraining (briefly) on occasions and, with very few exceptions, no Exetel user has ever noticed that their P2P downloads were affected in any way – as indeed in the full scheme of things they weren’t. Our own (Exetel personnel only) trials show that the likely maximum impact for any single P2P download will be around 15% which, at least in Australia, is lost in the customary erratic download speeds achieved by using P2P programs.”

Exetel’s approach to the ever bandwidth hungry P2P market shows there’s more than one solution to this situation. Some ISPs choose to completely throttle bandwidth, other implement caching. Exetel is mindful of the growing importance of file-sharing, and the importance its customers place on its continued availability. With a customer base of over 40,000, Exetel chose the path that will in all likelihood keep most of its customers happy.